Transfer line coke calciner



May 24, 1966 E. AQ DESTREMPS TRANSFER LINE COKE CALCINER Filed June 9,1961 AIR- AIR BLOWER FURNACE COKE TRANS FUEL GAS FER LINE CALCINER 17'iI WATER STEAM WATER FLUE GAS CYCLONE CALCINED Edward A. Desfremps COKEPoTentArtorney United States Patent 3,252,871 TRANSFER LINE COKECALCINER Edward A. Destremps, Murray Hill, NJ., assignor to EssoResearch and Engineering Company, a corporation of Delaware Filed June9, 1961, Ser. No. 116,122 5 Claims. (Cl. 201-17) This invention relatesto a process and apparatus for the calcination of coke particles made ina fluid coking process. More particularly, the invention relates to asingle-stage calcination process and apparatus wherein fluid cokeparticles are suspended in a gaseous medium, rapidly heated to acalcination temperature, and the gaseous suspension of coke particles isthen cooled or quenched before the coke is separated from the suspendinggaseous medium.

Fluid coke is produced as one product in the fluid coking process forthe conversion of residual petroleum oils and the like to lower boilinghydrocarbons, such as gas oil. The fluid coking process is described inPfeiifer et al., US. Patent 2,881,130, granted April 7, 1959. Varioususes have been suggested for the fluid coke particles which have aparticle size between about 150 and 250 microns on the average. Toimprove the quality of the fluid coke particles, it is necessary tocalcine the coke particles, i.e., they are heated to a temperaturebetween about 1600 F. and 3000 F. to remove volatile materials from thecoke particles, the heating being relatively prolonged if the cokeparticles contain a high percentage of sulfur. Calcination increases thedensity of the coke particles and lowers their electrical resistivity.The combustible volatile material released during calcination is burnedin preference to the coke product and so helps in supplying heat tofluid coke particles in the calcination vessel.

Various methods for the calcination of coke from the fluid cokingprocess have been devised. One type of process involves the use of atransfer line burner wherein the fluid coke in a gas suspension israpidly heated to a temperature up to about 25 00 F., the purpose ofthis being to devolatilize the coke. The hot mixture of coke and gasesis then passed to a cyclone separator where the hot fluid coke particlesare separated from the gases. Following this, the separated hot cokeparticles may be conveyed to a heat soaker where they are retained for aperiod of time at a high temperature to complete the devolatilizationprocess. A great disadvantage of this process resides in the fact thatsince, the coke leaves the transfer line at a temperature of about 2500F., the cyclone separator to which it is conveyed must be built ofextremely expensive heat-resistant materials. Furthermore, the cyclonemust be very large since at 2500 F., the volume of the gases leaving thetransfer line is very great.

It is proposed in this invention to cool or quench the calcined cokeparticles before they pass from the transfer line to the cycloneseparator or other separating means. This will reduce the temperatureand volume of the solid-gas suspension so that a smaller,conventionally-constructed cyclone of much lower cost may be used.Although it would be impossible to heat soak this cooled coke, it hasbeen found that heat soaking is unnecessary to produce coke of highdensity and low electrical resistivity if the coke has a low sulfurcontent.

It is an object of this invention to calcine fluid coke in asingle-stage process by heating it rapidly in a high velocity transferline heater.

It is a further object of this invention to minimize the combustion ofcoke in the transfer line by adding extraneous fuel thereto.

Another object of this invention is to permit the use 3,252,871 PatentedMay 24, 1966 of a conventionally-constructed cyclone separator or thelike in the calcination process by cooling or quenching the coke as itleaves the transfer line and before it is introducedinto the cycloneseparator.

Other objects and advantages of the invention will become apparentduring the course of the following description and discussion of theaccompanying drawing.

Referring now to the drawing, coke, which may be cold or at atemperature of about 1000 F. as it comes from a fluid coke burner, isintroduced into the upper portion of transfer line burner or heater 16through line 13. While the transfer line burner is shown as verticallyarranged, itcan be inclined at any angle or even horizontally arranged.The embodiment of the invention indicated in the drawing indicates adownflow; however, it is possible alternatively to arrange the apparatusso that the gaseous-solid suspension flows upwardly, or flows at anyangle to the horizontal, including horizontal flow itself.

Transfer line burner 16 may be between 20 and 100 feet long, preferablybetween about 30 and feet long. In the specific example, it is 60 feetlong. Its inside diameter may be any size within practical limits ofconstruction and depends on coke feed rate. Any coke feed rate ispossible, although this example predicates a feed rate of about 200 tonsper day, and an inside diameter of burner 16 of about 3 /2 feet. Betweenabout 3500 and 4000 s.c.f.m of air leaves blower 10 and after itstemperature is raised to about 1000 F. to 1300 F. in furnace 11, theheated air is introduced into the upper portion of the transfer lineburner through line 12. If desired, the air need not be preheated andmay be utilized at room temperature by being passed around furnace 11through line 12'. Between about 150 and 300 s.c.f.m. of a gaseous fuelsuch as methane, natural gas, or the like enters the upper portion oftransfer line burner 16 through one or more branched, vertically spacedlines 14- and 15. Line 14 discharges into the upper portion of burner 16and line 15 discharges lower down and into an intermediate portion ofburner 16. The mixture of coke and gases forms a dispersed or dilutesuspension which is heated to between about 1600 F. and 3000 F. by thecombustion of the extraneously added gaseous fuel and the volatileproducts evolved from the coke particles as the suspension passes downthrough transfer line burner 16.

The velocity of the gas in the transfer line burner may be between about10 and feet per second; in the speciflc example, it is about 20 feet persecond. The velocity of the coke in said transfer line is between about10 and feet per second and while the coke residence time may vary in therange of 0.1 to 5 seconds, in the specific example it is about 2seconds. To maintain proper air concentration within transfer lineburner 16, air may be secondarily injected into the burner through line24 which taps line 12 and connects line 12 with an intermediate portionof burner 16, substantially in the region where line 15 injects fuel gasinto burner 16.

The concentrations of the solids-gas suspension passing down throughtransfer line burner 16 at the selected gas velocity of about 20 feetper second is about 0.9 lb. per lb. of gas, or the density is about 0.02lb. of coke per cubic foot of gas at 2600 F. and 2 atmospheres pressure.

The coke and gas suspension may be cooled by passing it through apreliminary quenching or cooling zone 17 in the lower portion of burner16 which may be of a simple water spray type where water is introducedthrough line 17'. The partly cooled coke suspension then passes downthrough a further cooling or quenching vessel 18 arranged at the bottomportion of burner vessel 16. Various methods of cooling are possible,such as the use of a water tube boiler or the introduction of cold coke.However, in the embodiment shown in the drawing, a waste heat tubularboiler having a bottom water inlet 18 and a top steam outlet 18" isutilized. The coke/ gas mixture flows down through the tubes 18",transferring heat by indirect heat exchange to water on the outside ofthe tubes. If desired, a waste heat boiler can be used where the coke/gas mixture is on the outside of the tubes and the water to be heatedand vaporized is on the inside of the tubes.

The coke/ gas mixture remains in quenching or cooling zone 17 for about0.5 to 1.0 second and is cooled to a temperature between about 400 F.and 1600 F., preferably about 400 F. to 500 F. Approximately 28 gallonsper minute of water enter line 18 and about 14,000 lbs. per hour ofsteam are taken off through the line 18". The coke/gas mixture orsuspension then passes down from boiler 18 through conical bottom 19,and then through line 19 into cyclone separator 20 where the cooled cokesolids are separated from the entraining gases. Combustion gases arewithdrawn overhead through line 21 and the product calcined coke iswithdrawn through dipleg 22. This coke can be further cooled by indirectheat exchange in a waste heat boiler, by water quenching, or by anyother conventional means.

The diagrammatic showing omits many features which those skilled in theart would recognize as desirable or essential in actual plant operation.These omissions are made in order to simplify the presentation of theinvention and to avoid encumbering it with well understood engineeringdetails.

This invention eliminates the conventional heat soaking stage found inprocesses of a similar type. It has been found that this heat soakingstep is of very little value if desulfurization is not required. Such isthe case if the coke is made from a low sulfur residual stock so that itcontains less than about 2 wt. percent sulfur.

The data presented below show how quickly the volatile material isremoved from the coke and how quickly the density is increased. The dataalso show how little the properties of such fluid coke particles may beim proved by heat soaking after calcination in a transfer line burner.

In the examples shown, coke from the fluid coking process having aparticle size between about 150 and 250 microns on the average was mixedwith methane and air, and the suspension was passed through a foot longhorizontal transfer line wherein it was heated to a temperature of about2400 F. for about 0.5 to 2.0 seconds. A portion of this coke wasseparated from the gases with which it was mixed by the use of a cycloneseparator and was then passed to a heat soaker, while a separate portionwas rapidly cooled to a temperature of about 400F. after being separatedfrom the gases with which it was mixed by means of a cyclone separator.Both portions of coke were tested to indicate the volatile content,density, and electrical resistivity of the coke particles. The headingCoke Temperature, F. refers to the temperature of the coke at the exitof the transfer line; V=volatile content, wt. percent; D=density,gms./cc.; R=electrical resistivity, ohm-inch l0 at 500 p.s.i.

RUN NUMBER 1 Coke rate, 8.8lbs./n1in.

Air rate, 27.7 lbs/min.

Gas rate, 0.39 lb./min.

Coke temperature, I"., 2,220.

4 RUN NUMBER 2 Coke rate, 8.0 lbs/min.

Air rate, 29.0lbs./1nin.

Gas rate, 0.87 lbJinin.

Coke temperature, F., 2,470.

Coke properties V D R Raw coke 4. 30 1. 51 m At exit of transfer line 0.60 1. 76 31 After 60 min. soak. 0. 60 1. 27 After min. s0ak 0. 5O 1. 7725 RUN NUMBER 3 Coke rate, 6.8 lbs/min.

Air rate, 29.5 lbs/ruin.

Gas rate, 0.9 lb./1nin.

Coke temperature, F., 2,610.

Coke properties V l D i B Row coke 5. 50 1. 55 m At exit of transferline- 0. 34 1. 71 36 After 60 min. soak 0. 64 l. 79 34 After 120 min.soak 0.37 1.81 32 By the time the coke reached the end of the transferline, it had attained, for all practical purposes, its final physicalform. Heat soaking changed the properties very little. Therefore, it maybe seen from the data that a short-time, single-stage, high-temperaturecalcination process utilizing a transfer line burner as described can beused to produce coke with satisfactory properties despite theelimination of the heat soaking step.

This invention has been described with certain specific embodiments;however, it should be understood that these are by way of example ratherthanby way of limitation and it is not intended that the invention berestricted thereby, but only by the scope of the appended claims.

What is claimed is:

1. A process for calcining coke particles made in a fluid coke processto rapidly remove volatile matter and to rapidly increase the density ofthe coke solid particles which comprises the steps of rapidly heatingthe coke particles containing less than about 2 weight percent of sulfurand while in the form of a high velocity dispersed gaseous suspensionpassing through a transfer line heating zone to a temperature in therange of about 1600 F. to 3000 F. in about 0.1 to 5.0 seconds by thecombustion initially of an added gaseous extraneous fuel with anoxygen-containing gas, then immediately and rapidly cooling saiddispersion of coke particles adjacent the exit of said transfer lineheating zone in a cooling or quenching zone to a temperature in therange of about 400 F. to 500 F., then separating the cooled cokeparticles from the suspending flue gas, and then withdrawing the cooledand calcined coke particles from the separating step.

2. A process according to claim 1 wherein the dispersed suspension ofcoke particles contains about 0.2 to 2.0 lbs. of coke per pound of gas.

3. A process for calcining fluid coke solid particles to rapidly removevolatile matter and to rapidly increase the density of the coke solidparticles which includes introducing said coke solids containing lessthan about 2 weight percent of sulfur into one end of a high velocitytransfer line burning zone, adding gaseous fuel to said burning zone,injecting air into said burning zone to burn said fuel and form a hotgaseous suspension of said coke solids while moving it through saidburning zone, burning said gaseous fuel in said zone to heat said movingcoke solids suspension to a temperature between about 1600 F. and 3000F. in about 0.1 to 5.0 seconds, then immediately discharging the heatedgaseous suspension of coke solids from the other end of said burningzone and rapidly cooling said coke solids suspension adjacent 5 theother end of said burning zone to a temperature between about 400" F.and 500 F., and then passing said cooled coke solids gaseous suspensionto a solids separating zone to remove cooled calcined coke solids fromthe suspending gases.

4. A process according to claim 3 wherein the temperature in saidtransfer line burning zone is about 2400 F., the residence time of saidsuspension in said burning zone is about 2.0 seconds and the suspensionof said coke solids is rapidly cooled to about 400 F.

5. A process according to claim 3 wherein the gaseous suspension of cokesolids contains about 0.2 to 2.0 lbs. of coke per pound of gas and thetime of quenching is about 1 second.

6 References Cited by the Examiner UNITED STATES PATENTS 2,366,05712/1944 Russell 20237 2,564,700 8/1951 Krejci 23-2094 2,881,130 4/1959Pfeiffer et a1 208127 2,964,464 12/1960 Smith et a1. 20231 2,998,3548/1961 Brown et a1. 20231 0 MORRIS O. WOLK, Primary Examiner.

ALPHONSO D. SULLIVAN, DELBERT E. GANTZ,

Examiners.

I. H. HALL, I. H. TAYMAN, ]R., Assistant Examiners.

1. A PROCESS FOR CALCINING COKE PARTICLES MADE IN A FLUID COKE PROCESSTO RAPIDLY REMOVE VOLATILE MATTER AND TO RAPIDLY INCREASE THE DENSITY OFTHE COKE SOLID PARTICLES WHICH COMPRISES THE STEPS OF RAPIDLY HEATINGTHE COKE PARTICLES CONTAINING LESS THAN ABOUT 2 WEIGHT PERCENT OF SULFURAND WHILE IN THE FORM OF A HIGH VELOCITY DISPERSED GASEOUS SUSPENSIONPASSING THROUGH A TRANSFER LINE HEATING ZONE TO A TEMPERATURE IN THERANGE OF ABOUT 1600*F. TO 3000*F. IN ABOUT 0.1 TO 5.0 SECONDS BY THECOMBUSTION INITIALLY OF AN ADDED GASEOUS EXTRANEOUS FUEL WITH ANOXYGEN-CONTAINING GAS, THEN IMMEDIATELY AND RAPIDLY COOLING SAIDDISPERSION OF COKE PARTICLES ADJACENT THE EXIT OF SAID TRANSFER LINEHEATING ZONE IN A COOLING OR QUENCHING ZONE TO A TEMPERATURE IN THERANGE OF ABOUT 400*F. TO 500*F., THEN SEPARATING THE COOLED COKEPARTICLES FROM THE SUSPENDING FLUE GAS, AND THEN WITHDRAWING THE COOLEDAND CALCINED COKE PARTICLES FROM THE SEPARATING STEP.